The present invention relates to a method of manufacturing miniaturized devices.
Lithographic processes are commonly used in the manufacture of miniaturized structures such as integrated circuits, liquid crystal elements, micro-patterned structures and micro-mechanical components.
A projection exposure apparatus used for photolithography generally comprises a projection optical system for imaging a patterning structure, commonly referred to as a reticle, onto a substrate, commonly referred to as a wafer. The substrate (wafer) is coated with a photo-sensitive layer, commonly referred to as a resist, which is exposed with the image of the patterning structure using imaging light. The imaging light is generated by an illumination optical system illuminating the patterning structure.
The trend to produce even smaller and more sophisticated miniaturized devices places increasingly high demands on the projection exposure system. Such demands include a high quality of the imaging of the patterning structure onto the wafer. In particular, imaging characteristics, such as imaging aberrations, such as a coma, field curvature and others, should be low. One further imaging characteristics is a telecentricity of the imaging. A preferred imaging optics is a telecentric optics which means that main rays or chief rays of imaging light passing through an image plane of the imaging optics are parallel to an optical axis of the imaging optics. In such situation, positions of patterns imaged on the substrate will substantially not depend on a position of the substrate along the optical axis within the depth of focus of the system. Therefore, it is desired to adjust a telecentricity of the projection exposure system such that the imaging of the pattern onto the substrate is a telecentric imaging.
From U.S. Pat. No. 5,499,100 and U.S. Pat. No. 5,739,899 there are known projection optical systems allowing to determine a telecentric property of the imaging optics and to adjust characteristics of the projection exposure system such that a telecentric property of the imaging is improved.
It has been found that the conventional methods using a projection exposure system allowing detection and adjustment of telecentric properties still provides an insufficient quality of the imaged patterns.